As it is generally known, aircrafts, in particular helicopters or convertiplanes, may need to operate in a condition of limited in-flight visibility.
This limited visibility may be due, for example, to dust or sand in the air, when the aircraft operates in a desert area.
In this case, the resulting limited visibility condition is generally known as “brownout”.
A further kind of limited visibility condition is the so-called “whiteout” condition, in which visibility and contrast are severely reduced.
Whiteout may be due to heavy snowfall rates or to diffuse lighting from overcast cloud, mist or fog, or a background of snow.
Both the conditions are likely to cause accidents, especially during landing or take-off operations.
These accidents are mainly due to the fact that the pilot cannot see surrounding objects, which usually provide the outside visual references necessary to control the aircraft near the ground. As a result, the pilot can be spatially disoriented and lose the awareness and the promptness necessary to properly control the aircraft.
Furthermore, the pilot is likely to lose any visual perception of the horizon and/or to fall into physical and mental instability.
The above situation is likely to generate a risk of side slipping of the aircraft.
In the case of helicopters or convertiplanes, intense dust clouds stirred up by the rotor downwash during near-ground flight may cause significant flight safety risks, thus dramatically increasing the risk of accidents.
A need is felt within the sector to reduce as far as possible the risks of accidents when the aircraft is operated in conditions of in-flight limited visibility, especially in “brownout” or “whiteout” conditions.
A need is also felt, during other delicate maneuver, e.g. mountain rescue operations, to provide the pilot with key flight data without requiring him to look down the instrument console.
WO2005/015333 discloses a flight control system for aircrafts capable of vertical take off and landing.
In greater detail, the flight control system is adapted to facilitate flying in conditions of restricted visibility and substantially comprises: a series of sensors for receiving environmental information, and a central processing unit that combines the environmental information received from the with mission-specific information.
The central processing unit filters the environmental information and converts it into a visual format which may be implemented either in a head-mounted display or in a head up display.
US-A-2009/0265060 discloses a method for operating a brownout/obscured landing system. The method comprises the steps of receiving data indicating aircraft position, displaying a three-dimensional perspective grid on a map and electronically moving the grid on the display in response to the aircraft position.
In particular, the map is displayed on a pilot kneeboard.
US-A-2006087542 discloses a method and a system for supporting pilots in landing helicopter in visual flight under brownout or whiteout conditions. In detail, three-dimensional data of the planned landing site are generated during the approach for landing, and are accumulated in a three-dimensional representation of the landing site. A virtual external view is continuously generated from this three-dimensional representation and displayed to the pilot.
EP-A-1906151 discloses an imaging and display system which provides helicopter pilots with an unobstructed display of a landing area in whiteout or brownout conditions, by capturing a high resolution image of the landing area prior to obscuration.